The present invention relates generally to a satellite trunked radio service system for satellite communication, and more particularly, to a satellite trunked radio service system for satellite communication utilizing a shared satellite demand circuit associated with voice networks.
Wireless technology is not new. The age of electronic communication began with the invention of a practical telegraph in 1844, over 150 years ago. It has been said that the telegraph was a major factor in the explosive development of the Western United States in the mid-1800""s.
In 1983, the FCC issued licenses to provide mobile communications in a new frequency hand using a technique called cellular transmission which had been developed by both ATandT and Motorola. The proponents invested over $400 million in the new business before the FCC licensed cellular service. Many people thought that consumers needed mobile communications as much as they needed a second Jaguar automobile. Much to the surprise of everyone the growth rate was phenomenal. An enormous mass market developed for this service.
There are over 500 million users of wireline communications in the world today. By the early part of the next century, wireline will continue to grow, and wireless will be a major factor in telecommunications. According to the U.S. Commerce Department, there are at least 52 million cellular subscribers in the world (23 million in the U.S.). Within five years, experts estimate that there may be 150 million (50 million U.S.) and by 2005 we expect the worldwide total will be 260 million (65 million U.S.).
Cellular service is available in most urban regions, excluding, large, less developed areas. Service is not provided beyond the range of cells at which distances the signals are too weak. Cells typically do not exceed 10 miles in diameter, although super large cells have been created in the Caribbean. The new PCS service, which operates at much higher frequencies, requires even smaller cells, three times as many cells must be built as are required for cellular service. In regions where population density is low, the cost of building and operating transmission facilities may exceed the potential revenues. Wireless is sometimes blocked by terrain even in highly populated regions because the transmission signal arrives at low elevation angles.
Surveys show that customers currently are unhappy with unavailability and call blockage. Because of the low elevation angle transmission, service is sometimes interrupted during transmission or handover from cell to cell. During the peak busy hours, circuits are often blocked by other callers. Subscribers would like to enjoy wireless service all of the time, wherever they are.
Another major problem is that wireless transmission standards differ throughout the world. International travelers ar required to use different telephones when they travel to other regions. Even within the U.S. the new digital cellular service will be based on both time division multiple access (TDMA) and code division multiple access (CDMA) technology. Current plans suggest that digital cellular customers who roam up the East Coast will travel alternatively between systems that use different access methods.
Most of the world""s telephone service is concentrated in the industrialized world. The 800 million people in industrialized countries have access to 400 million telephone lines, but 5 billion people in developing countries have access to only 200 million telephone lines. In Asia, more than 3 billion people have only 75 million telephone lines, and in Africa, with 500 million people, there is only one telephone per 1000 population.
The cost of closing the gap in developing countries has been estimated to be $3 trillion. Space based services are a faster and less costly solution. Large regions that are not served today could be economically served in the future with satellites. New systems hold the potential for extending service into regions that have been inaccessible or uneconomical to serve because of low population density or weak economic conditions.
Even in affluent, densely populated countries like Japan nd Germany, mountainous conditions prevent full coverage. Japanese cellular service operators expect that half of the land area will not be covered by terrestrial wireless. We are on the threshold of being able to provide universal, affordable wireless service throughout the world.
Wireless service is more expensive than wireline service, especially in urban regions. From a service provider perspective, the cost is higher because the call routing, call maintenance and billing is more complex. From a subscriber perspective, wireless telephone service adds great value. Wireless telephones allow mobile workers to talk while traveling. Mobile calls provide greater flexibility and permit communications in situations in which they were previously impossible.
Today, cellular systems offer service with a wide range of tariffs. typically, the systems charge a monthly service fee of about $30 plus an additional charge based on airtime. For local services, the airtime rates vary between $0.10 to $0.90 per minute, depending on the region of the country or the world. Often, service providers offer cellular telephones at a discount but require a one year service contract, payment for the telephone equipment being embedded within the service price structure.
Currently, satellite service is available worldwide as an alternative to cellular service, but the terminal cost and service rates are very high. Inmarsat signatories offer service for airtime rates ranging from $5 to $15 per minute. xe2x80x9cPortablexe2x80x9d terminals that cost at least $15,000 and have a mass of 10 kilograms (22 pounds) can be lugged on trips. Terrestrial cellular has 1000 times more customers at service rates which are a factor of ten lower than present space based systems. The prices are very elastic.
Manufacturers of handsets and satellite systems recognized that cellular type communications from space could be much less expensive in the future than it is today. Several companies have determined that space based wireless service can be provided at service rates which are affordable by a mass market.
The primary consideration for business success is having a cost effective product which customers desire. This means balancing the service charges to own a personal telephone as well as the air time rates with the needs of the subscriber. Cost must also be kept affordable and economical compared to alternatives. However, each system must strike a balance between low cost and high quality. As a business, the service and distribution functions must provide an outlet to the ultimate customer, the consumer.
In the mid 1960""s we had correctly determined that the best orbit for fixed satellite service was a geostationary orbit. This choice was logical because a stationary orbit permitted satellites to appear fixed in the sky. Large, high gain ground terminals could be positioned to ensure that the transmission path always would be clear. Although large, the antennas had no need to track, since the satellites appeared motionless to it. Only three or four satellites were needed to view most of the globe (excepting the polar regions). Unfortunately, the distance to Geostationary Earth Orbit (GEO) is great (about 23,000 miles) and the propagation time delay produces overtalking and confusion.
During the 1980""s, conditions developed for a major change in the satellite communications paradigm: Orbiting satellites closer to the Earth would permit more powerful transmission with reasonable sized satellites and antennas. In addition, inclined orbits could ensure high elevation angles to minimize blockage by buildings, and other obstacles. The microelectronics for a ground station had become so compact that an affordable, light, hand held terminal could be built for satellite service. The lower power, application specific integrated circuit (ASIC) was built with GaAs, High density Bipolar Transistors (HBT) and high electron mobility power transistors (HEMPT""s).
A conceptual overview of the satellite network system is illustrated conceptually in FIG. 1. The satellite network system design provides the capability for METs and FESs to access one or more multiple beam satellites located in geostationary orbit to obtain communications services.
The heart of the satellite network system for each of the networks is the Network Control System (NCS) which monitors and controls each of the networks. The principal function of the NCS is to manage the overall satellite network system, to manage access to the satellite network system, to assign satellite circuits to meet the requirements of mobile customers and to provide network management and network administrative and call accounting functions.
The satellites each transmit and receive signals to and from METs at L-band frequencies and to and from Network Communications Controllers (NCCs) and Feederlink Earth Stations (FESs) at Ku-band frequencies. Communications at L-band frequencies is via a number of satellite beams which together cover the service area. The satellite beams are sufficiently strong to permit voice and data communications using inexpensive mobile terminals and will provide for frequency reuse of the L-band spectrum through inter-beam isolation. A single beam generally covers the service area.
The satellite network system provides the capability for mobile earth terminals to access one or more multiple beam satellites located in geostationary orbit for the purposes of providing mobile communications services. The satellite network system is desired to provide the following general categories of service:
Mobile Telephone Service (MTS). This service provides point-to-point circuit switched voice connections between mobile and public switched telephone network (PSTN) subscriber stations. It is possible for calls to be originated by either the mobile terminal or terrestrial user. Mobile terminal-to-mobile terminal calls are also supported.
Mobile Radio Service (MRS). This service provides point-to-point circuit switched connections between mobile terminal subscriber stations and subscriber stations in a private network (PN) which is not a part of the PSTN. It is possible for calls to be originated from either end. Mobile terminal-to-mobile terminal calls are also supported.
Mobile Telephone Cellular Roaming Service (MTCRS). This service provides Mobile Telephone Service to mobile subscribers who are also equipped with cellular radio telephones. When the mobile terminal is within range of the cellular system, calls are serviced by the cellular system. When the mobile terminal is not in range of the cellular system, the MTCRS is selected to handle the call and appears to the user to be a part of the cellular system. When the mobile terminal is not in range of the cellular system, the MTCRS is selected to handle the call and appears to the user to be a part of the cellular system. It is possible for calls to be originated either from the MET or the PSTN. Mobile terminal-to-mobile terminal calls are also supported.
Mobile Data Service (MDS). This service provides a packet switched connection between a data terminal equipment (DTE) device at a mobile terminal and a data communications equipment (DCE)/DTE device connected to a public switched packet network. Integrated voice/data operation is also supported.
The satellites are designed to transmit signals at L-band frequencies in the frequency band 1530-1559 MHz. They will receive L-band frequencies in the frequency band 1631.5-1660.5 MHz. Polarization is right hand circular in both bands. The satellites will also transmit in the Ku frequency band, 10,750 MHz to 10,950 MHz, and receive Ku-band signals in the frequency band 13,000 to 13,250 MHz.
The satellite transponders are designed to translate communications signals accessing the satellite at Ku-band frequencies to an L-band frequency in a given beam and vice versa. The translation will be such that there is a one-to-one relation between frequency spectrum at Ku-band and frequency spectrum in any beam at L-band. The satellite transponders will be capable of supporting L-band communications in any portion of the 29 MHz allocation in any beam.
Transponder capacity is also provided for Ku-band uplink to Ku-band down-link for signalling and network management purposes between FESs and NCCs. The aggregate effective isotropic radiated power (AEIRP) is defined as that satellite e.i.r.p. that would result if the total available communications power of the communications subsystem was applied to the beam that covers that part of the service area. Some of the key performance parameters of the satellite are listed in FIG. 2.
The satellite network system interfaces to a number of entities which are required to access it for various purposes. FIG. 3 is a context diagram of the satellite network system conceptually illustrating these entities and their respective interfaces. Three major classes of entities are defined as user of communications services, external organizations requiring coordination, and network management system.
The users of satellite network communications services are MET users who access the satellite network system either via terrestrial networks (PSTN, PSDN, or Private Networks) or via METs for the purpose of using the services provided by the system. FES Owner/Operators are those organizations which own and control FESs that provide a terrestrial interface to the satellite network. When an FES becomes a part of the satellite network, it must meet specified technical performance criteria and interact with and accept real-time control from the NCCs. FES Owner/Operators determine the customized services that are offered and are ultimately responsible for the operation and maintenance of the FES. Customers and service providers interact with the Customer Management Information System within the Network Management System.
The satellite network system interfaces to, and performs transactions with, the external organizations described below:
Satellite Operations Center (SOC)
The SOC is not included in the satellite network ground segment design. However, the satellite network system interfaces with the SOC in order to maintain cognizance of the availability of satellite resources (e.g. in the event of satellite health problems, eclipse operations, etc.) and, from time to time, to arrange for any necessary satellite reconfiguration to meet changes in traffic requirements.
NOC
The satellite network system interfaces with the satellites located therein via the NOC for a variety of operational reasons including message delivery and coordination.
Independent NOCs
The satellite network system interfaces with outside organizations which lease resources on satellite network satellites and which are responsible for managing and allocating these resources in a manner suited to their own needs.
Other System NOCs
This external entity represents outside organizations which do not lease resources on satellite network satellites but with whom operational coordination is required.
The satellite network management system (NMS) is normally located at an administration""s headquarters and may comprise three major functional entities; Customer Management Information System (CMIS), Network Engineering, and System Engineering (NE/SE). These entities perform functions necessary for the management and maintenance of the satellite network system which are closely tied to the way the administration intends to do business. The basic functions which are performed by CMIS, Network Engineering, and System Engineering are as follows:
Customer Management Information System
This entity provides customers and service providers with assistance and information including problem resolution, service changes, and billing/usage data. Customers include individual MET owners and fleet managers of larger corporate customers. Service providers are the retailers and maintenance organizations which interact face to face with individual and corporate customers.
Network Engineering
This entity develops plans and performs analysis in support of the system. Network Engineering analyzes the requirements of the network. It reconciles expected traffic loads with the capability and availability of space and ground resources to produce frequency plans for the different beams within the system. In addition, Network Engineering defines contingency plans for failure situations.
System Engineering
This entity engineers the subsystems, equipment and software which is needed to expand capacity to meet increases in traffic demands and to provide new features and services which become marketable to subscribers.
The satellite network system comprises a number of system elements and their interconnecting communications links as illustrated conceptually in FIG. 4. The system elements are the NOC, the NCC, the FES, the MET, the Remote Monitor Station (RMS), and the System Test Station (STS). The interconnecting communications links are the satellite network Internetwork, terrestrial links, the MET signaling channels, the Interstation signaling channels, and the MET-FES communications channels. The major functions of each of the system elements are as follows:
NOC
The NOC manages and controls the resources of the satellite network system and carries out the administrative functions associated with the management of the total satellite network system. The NOC communicates with the various internal and external entities via a local area network (LAN)/wide area network (WAN) based satellite network Internetwork and dial-up lines.
NCC
The NCC manages the real time allocation of circuits between METs and FESs for the purposes of supporting communications. The available circuits are held in circuit pools managed by Group Controllers (GCs) within the NCC. The NCC communicates with the NOC via the satellite network Internetwork, with FESs via Ku-to-Ku band interstation signaling channels or terrestrial links, and with mobile terminals via Ku-to-L band signaling channels.
FES
The FES supports communications links between METs, the PSTN, private networks, and other MTs. Once a channel is established with an MET, call completion and service feature management is accomplished via In-Band signaling over the communication channel. Two types of FESs have been defined for the satellite network system; Gateway FESs and Base FESs. Gateway FESs provide MTS, MRS, MTCRS and NR services. Base FESs are for like services and/or value added services.
MET
The MET provides the mobile user access to the communications channels and services provided by the satellite network system. A range of terminal types has been defined for the satellite network system.
RMS
The RMS monitors L-band RF spectrum and transmission performance in specific L-band beams. An RMS is nominally located in each L-band beam. Each RMS interfaces with the NOC via either a satellite or terrestrial link.
STS
The STS provides an L-band network access capability to support FES commissioning tests and network service diagnostic tests. The STS is collocated with, and interfaced to, the NOC.
Communications channels transport voice, data and facsimile transmissions between METs and FESs via the satellite. Connectivity for MET-to-MET calls is accomplished by double hopping the communications channels via equipped FESs. Signaling channels are used to set up and tear down communications circuits, to monitor and control FES and MET operation, and to transport other necessary information between network elements for the operation of satellite network. The system provides Out-of-Band and Interstation signaling channels for establishing calls and transferring information. In-Band signaling is provided on established communications channels for supervisory and feature activation purposes. A detailed description of the satellite network signaling system architecture is provided in L. White, et al., xe2x80x9cNorth American Mobile Satellite System Signaling Architecture,xe2x80x9d AIAA 14th International Communications Satellite Conference, Washington, D.C. (March 1992), incorporated herein by reference.
The satellite network Internetwork provides interconnection among the major satellite network ground system elements such as the NOCs, NCCs, and Data Hubs, as well as external entities. Various leased and dial-up lines are used for specific applications within the satellite network system such as backup interstation links between the NCC and FESs and interconnection of RMSs with the NOC.
The primary function of the NOC is to manage and control the resources of the satellite network system. FIG. 5 is a basic conceptual block diagram of the NOC and its interfaces. The NOC computer is shown with network connections, peripheral disks, fault tolerant features, and expansion capabilities to accommodate future growth. The NOC software is represented as two major layers, a functional layer and a support layer. The functional layer represents the application specific portion of the NOC software. The support layer represents software subsystems which provide a general class of services and are used by the subsystems in the functional layer.
The application specific functions performed by the NOC are organized according to five categories: fault management, accounting management, configuration management, performance management, and security management. The general NCC Terminal Equipment (NCCTE) configuration showing constituent equipment includes: processing equipment, communications equipment, mass storage equipment, man-machine interface equipment, and optional secure MET Access Security Key (ASK) storage equipment. The Processing Equipment consists of one or more digital processors that provide overall NCC control, NCS call processing, network access processing and internetwork communications processing.
The Communications Equipment consists of satellite signaling and communications channel units and FES terrestrial communication link interface units. The Mass Storage Equipment provides NCC network configuration database storage, call record spool buffering an executable program storage. The Man-Machine Interface Equipment provides operator command, display and hard copy facilities, and operator access to the computer operating systems. The MET ASK storage Equipment provides a physically secure facility for protecting and distributing MET Access Security Keys.
The NCCTE comprises three functional subsystems: NCCTE Common Equipment Subsystem, Group Controller Subsystem, and Network Access Subsystem. The NCCTE Common Equipment subsystem comprises an NCC Controller, NCCTE mass storage facilities, and the NCCTE man-machine interface. The NCC Controller consists of processing and database resources which perform functions which are common to multiple Group Controllers. These functions include satellite network Internetwork communications, central control and monitoring of the NCCTE and NCCRE, storage of the network configuration, buffering of FES and Group Controller call accounting data, transfer of transaction information to the Off-line NCC and control and monitoring of FESs.
The Mass Storage element provides NCC network configuration database storage, call accounting data spool buffering, and NCCTE executable program storage. The Man-machine Interface provides Operator command and display facilities for control and monitoring of NCC operation and includes hard copy facilities for logging events and alarms. A Group Controller (GC) is the physical NCC entity consisting of hardware and software processing resources that provides real time control according to the CG database received from the NOC.
The Group Controller Subsystem may incorporate one to four Group Controllers. Each Group Controller maintains state machines for every call in progress within the Control Group. It allocates and de-allocates circuits for FES-MET calls within each beam of the system, manages virtual network call processing, MET authentication, and provides certain elements of call accounting. When required, it provides satellite bandwidth resources to the NOC for AMS(R)S resource provisioning. The Group Controller monitors the performance of call processing and satellite circuit pool utilization. It also performs MET management, commissioning and periodic performance verification testing.
The Network Access Subsystem consists of satellite interface channel equipment for Out-of-Band signaling and Interstation Signaling which are used to respond to MET and FES requests for communications services. The Network Access Processor also includes MET communications interfaces that are used to perform MET commission testing. In addition, the subsystem includes terrestrial data link equipment for selected FES Interstation Signaling.
The principal function of the FES is to provide the required circuit switched connections between the satellite radio channels, which provide communications links to the mobile earth terminals, and either the PSTN or PN. FESs will be configured as Gateway Stations (GS) to provide MTS and MTCRS services or Base Stations to provide MRS and Net Radio services (described in detail below). Gateway and Base functions can be combined in a single station.
The FES operates under the real time control of the Network Communications Controller (NCC) to implement the call set-up and take-down procedures of the communications channels to and from the METs. Control of the FES by the NCC is provided via the interstation signaling channels. An FES will support multiple Control Groups and Virtual Networks. The FES is partitioned into two major functional blocks, the FES RF Equipment (FES-RE) and the FES Terminal Equipment (FES-TE). The principal function of the FES-RE is to provide the radio transmission functions for the FES. In the transmit direction it combines all signals from the communications and interstation signaling channel unit outputs from the FES-TE, and amplifies them and up-convert these to Ku-Band for transmission to the satellite via the antenna. In the receive direction, signals received from the satellite are down-converted from Ku-Band, amplified and distributed to the channel units within the FES-TE. Additional functions include satellite induced Doppler correction, satellite tracking and uplink power control to combat rain fades.
The principal function of the FES-TE is to perform the basic call processing functions for the FES and to connect the METs to the appropriate PSTN or PN port. Under control of the NCC, the FES assigns communications channel units to handle calls initiated by MET or PSTN subscribers. The FES-TE also performs alarm reporting, call detail record recording, and provision of operator interfaces.
For operational convenience, an FES may in some cases be collocated with the NCC. In this event, the NCC RF Equipment will be shared by the two system elements and the interstation signaling may be via a LAN. Connection to and from the PSTN is via standard North American interconnect types as negotiated with the organization providing PSTN interconnection. This will typically be a primary rate digital interconnect. Connection to and from private networks is via standard North American interconnect types as negotiated with the organization requesting satellite network service. This will typically be a primary rate digital interconnect for larger FESs or an analog interconnect for FESs equipped with only a limited number of channels may be employed.
We have discovered that there is a general need for an integrated mobile telephone that can be used to transmit to, and receive from, to communicate in a Closed User Group (CUG) arrangement that allows each member of the group to hear what any other user is saying. Each member of the group can also talk when needed. The system behaves like a radio multi-party line where several parties communicate over the same communication channel. Public services and law enforcement agencies are typical users of this service, which is normally provided by either traditional terrestrial radio networks or by the more recent trunked radio systems. These trunked systems, generally in the 800-900 MHz band, provide groups of end users with virtual private systems by assigning frequencies to CUGs on a demand basis. In this connection, however, we have discovered that an integrated mobile communication device is needed that provides this ability to communicate in a CUG of a satellite network. Further, we have discovered that if this type of satellite trunking utilizes a shared satellite demand period circuit per CUG rather than one circuit per mobile user, the cost per minute of a group conversation would be much less expensive to the owner of the group.
We have further discovered that there is the need to provide the capability for the Closed User Group arrangement to be used alternately with a private point-to-point voice communication between two parties.
We have also discovered that for Closed User Group communications, additional security procedures are required to ensure that unauthorized parties are unable to enter the group. In this connection, we have discovered that an efficient method for permitting parties access to the Closed User Group without being to cumbersome is required.
We have also discovered that the call set-up time for one shared circuit per CUG compared to a mobile radio service multi-user conference set-up time is likely to be more acceptable to a group end user/operator, who normally expects to be able to talk as soon as the handset/microphone is taken off-hook. Further, we have discovered the need for a nationwide and regional point-to-multipoint mobile communication service that is not limited in coverage.
We have also discovered that there is a need to provide a procedure for priority service for the Closed User Group arrangement under a default mode. That is, we have discovered the need to permit a MET user while communicating in a first closed user group to have the capability to efficiently transmit a priority message to a predetermined closed user group.
It is a feature and advantage of the present invention to provide an integrated mobile telephone that can be used to transmit and receive in a Closed User Group (CUG) arrangement that allows each member of the group to hear what any other user is saying.
It is another feature and advantage of the present invention to permit each member of the group to talk when needed, and to provide a system that behaves like a radio multi-party line.
It is a further feature and advantage of the present invention to provide an integrated mobile communication device that can communicate in a CUG of a satellite network.
It is a further feature and advantage of the present invention to provide additional security procedures are required to ensure that unauthorized parties are unable to enter the group for the Closed User Group.
It is another feature and advantage of the present invention to provide an inexpensive satellite trunking service to the owner of the group.
It is another feature and advantage of the present invention to minimize the call set-up time for one shared circuit per CUG.
It is another feature and advantage of the present invention to provide a procedure for priority service for the Closed User Group arrangement under a default mode.
It is another feature and advantage to provide a MET user, while communicating in a first closed user group, to have the capability to efficiently transmit a priority message to a predetermined closed user group.
It is another feature and advantage of the present invention to generally effectively and efficiently effectuate transmissions between mobile communication devices and the satellite network in a closed user group environment by utilizing an efficient communication protocol.
It is another feature and advantage of the invention to provide the capability for the Closed User Group arrangement to be used alternately with a private point-to-point voice communication between two parties.
It is another feature and advantage of the invention to provide a nationwide and regional point-to-multipoint mobile communication service that is not limited in coverage.
The present invention is based, in part, on the desirability of providing point-to-multipoint circuit switched connections between mobile terminal subscriber stations and a central base station. Mobile users are able to listen to two-way conversations and to transmit using a push-to-talk mode of operation.
To achieve these and other features and advantages of the present invention, a mobile communication system is provided in a mobile satellite system. The mobile satellite system includes a satellite communication switching office having a satellite antenna for receiving/transmitting a satellite message via a satellite from/to a vehicle using a mobile communication system, a satellite interface system, a central controller receiving/transmitting the satellite message from/to the satellite communication switching office issued from the vehicle via the satellite and the satellite interface system. The mobile communication system includes a user interface system providing a user interface through which a user has access to services supported by the mobile satellite system, and an antenna system providing an interface between the mobile communication system and the mobile satellite system via the satellite interface system, and receiving a first satellite message from the satellite and transmitting a second satellite message to the satellite. The antenna system includes an antenna including one of a directional and an omnidirectional configuration, a diplexer, an amplifier, a low noise amplifier, a beam steering unit when the antenna is of the directional configuration, and at least one of a compass and sensor to determine vehicle orientation. The mobile communication system also includes a transceiver system, operatively connected to the antenna system, including a receiver and a transmitter. The transmitter converts the second satellite message including at least one of voice, data, fax and signaling signals into a modulated signal, and transmits the modulated signal to the antenna system. The transmitter includes an amplifier, a first converter and associated first frequency synthesizer, a modulator, an encoder, multiplexer, scrambler and frame formatter for at least one of voice, fax, and data. The receiver accepts the first satellite message from the antenna system and converts the first satellite message into at least one of voice, data, fax and signaling signals, at least one of the voice, data and fax signals routed to the user interface system. The receiver includes a second converter with an associated second frequency synthesizer, a demodulator, a decoder, demultiplexer, descrambler and frame unformatter for at least one of voice, fax, and data. The mobile communication system also includes a logic and signaling system, operatively connected to the transceiver, controlling initialization of the mobile communication system, obtaining an assigned outbound signaling channel from which updated system information and commands and messages are received. The logic and signaling system configures the transceiver for reception and transmission of at least one of voice, data, fax and signaling messages, and controls protocols between the mobile communication system and the mobile satellite system, and validating a received signalling messages and generating codes for a signaling message to be transmitted.
There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject matter of the claims appended hereto.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.
Further, the purpose of the foregoing abstract is to enable the U.S. Patent and Trademark Office and the public generally, and especially the scientists, engineers and practitioners in the art who are not familiar with patent or legal terms or phraseology, to determine quickly from a cursory inspection the nature and essence of the technical disclosure of the application. The abstract is neither intended to define the invention of the application, which is measured by the claims, nor is it intended to be limiting as to the scope of the invention in any way.
In one embodiment of the invention, a system for providing satellite communication between multiple users in a closed user group arrangement includes first and second mobile earth terminals (METs) responsively connected to and registering with the mobile satellite system. The first MET selects a closed user group network identifier (NET ID) representing a NET group including the first and second METs to establish voice communication therewith and transmits the NET ID to a central controller. The central controller receives the NET ID from the first MET, validates the first MET for communication, validates the NET ID, allocates a frequency for the NET group, and broadcasts the message to the NET group including the second MET informing the NET group of the allocated frequency and the voice communication associated therewith. The second MET tunes to the frequency in response to the message broadcast by the central controller, and the central controller assigns the first MET as current speaker for the NET group.
In another embodiment of the invention, a method of providing satellite communication between multiple users in a closed user group arrangement includes the steps of first and second mobile earth terminals (METs) registering with the mobile satellite system, the first MET selecting a closed user group network identifier (NET ID) representing a NET group including the first and second METs to establish voice communication therewith. The method also includes the steps of the first MET transmitting the NET ID to the central controller, the central controller receiving the NET ID, validating the first MET for communication, validating the NET ID, allocating a frequency for the NET group, and broadcasting the message to the NET group including the second MET informing the NET group of the allocated frequency and the voice communication associated therewith. The method also includes the steps of the second MET tuning to the frequency in response to the message broadcast by the central controller, and assigning by the central controller the first MET as current speaker for the NET group.
In another embodiment of the invention, the method also includes the step of monitoring by the first and second METs whether at least one of a dispatcher message, a priority message and a release of speaker message has been issued, and if so, interrupting the current speaker with the at least one of the dispatcher message, the priority message and a new speaker. The method also includes the steps of monitoring by the central controller whether the current speaker is active, and if not, removing the current speaker and setting the current speaker to vacant, notifying by the central controller the first and second METs that the current speaker is vacant, and initiating by one of the first and second METs a request to be the new speaker. The method further includes the steps of receiving by the central controller the request from a first of the one of the first and second METs to be the new speaker, and assigning the first of the one of the first and second METs as the new speaker, and releasing the closed user group communication when no request from the one of the first and second METs is made to be the new speaker for a predetermined period of time.
In another embodiment of the invention, the method also includes the steps of a third MET included in the NET group registering with the mobile satellite system, and the central controller broadcasting the message to the NET group including the third MET informing the NET group of the allocated frequency and the voice communication associated therewith. The method also includes the steps of the third MET tuning to the frequency in response to the message broadcast by the central controller by generating a scrambling vector for access thereto. The third MET gains access to the frequency and the voice communication of the NET group using the scrambling vector.
According to the invention, the central controller advantageously controls the closed user group satellite communication including net radio parameters used by the first and second METs. The central controller also selectively downloads the NET IDs to the first and second METs according to predetermined user criteria.
The central controller advantageously collects billing information regarding the closed user group satellite communication and transmits the billing information to the mobile satellite system. The mobile satellite system optionally charges a service fee to a customer that has requested the closed user group arrangement instead of each of the individual users in the NET group thereby consolidating the billing transactions and permitting a single customer to monitor communication charges.
In another embodiment of the invention, the method includes the steps of a non-MET accessing the mobile satellite system via either a public switched telephone network or a cellular network to initiate a closed user group communication with the NET group including at least one of the first and second METs, the central controller broadcasting the message to the NET group informing the NET group of the allocated frequency and the voice communication associated therewith, and the at least one of the first and second METs tuning to the frequency in response to the message broadcast by the central controller to communicate with the non-MET in the closed user group arrangement.
In another embodiment of the invention, the method includes the steps of the first MET selecting the closed user group network identifier (NET ID) representing a NET group including the first MET and a non-MET serviced by one of a public switched telephone network and a cellular network to establish voice communication therewith, and the first MET transmitting the NET ID to the central controller. Additionally, the method includes the central controller receiving the NET ID, determining that the NET group includes the non-MET, and broadcasting a non-MET message to either the public switched telephone network or the cellular network including the voice communication associated therewith, and either the public switched telephone network or the cellular network receiving the non-MET message from the central controller and transmitting the non-MET message to the non-MET to establish the closed user group arrangement between the MET and the non-MET.
The first MET beneficially includes a push to talk (PTT) device for generating the release of speaker message. The first MET activates the PTT device generating a PTT signal only when the PTT device is activated after the current speaker is vacant, relieving congestion on the satellite by selectively transmitting the PTT signal.
The central controller advantageously selectively downloads monitor codes to the first and second METs according to predetermined user criteria. The monitor code functions to lock the first and second METs to the NET group preventing the NET group from being released when no request has been made by the first or second METs to be the current speaker after the predetermined period of time.
In another embodiment of the invention, a priority default operation is provided. The first MET and the central controller implement the following operations:
(1) assigning, by the first MET, a default priority NET group for receiving a priority message when a priority button of the first MET is activated;
(2) activating, by the first MET, the priority button of the first MET to initiate the priority message to be transmitted to the default priority NET group even when the first MET is active in the NET group, wherein the default priority NET group is potentially different than the NET group;
(3) tuning, by the first MET, to a GC-S channel and transmitting a Net Radio Access Request Signalling Unit (NRACRSU) with a priority code appended on a corresponding receive channel indicating the default priority NET group;
(4) receiving, by the central controller, the NRACRSU and performing a MET originated NET Radio call setup procedure;
(5) rebroadcasting by the central controller the NET Radio Channel Assignment (NRCHASU) on the GC-S channel identified in the Net ID or that are active;
(6) transmitting by the central controller the NRCHASU a predetermined number of times in a predetermined number of consecutive superframes for a NET Radio channel assignment;
(7) setting by the central controller, the priority code and including a call identifier in the GC-I channel assignment message; and
(8) tuning, by the first MET, to the NET Radio channel assignment and proceeding with the voice communication.
In another embodiment of the invention, security measures are provided to prevent unauthorized METs from entering or accessing a closed user group communication. According to this aspect of the invention, a MET storing a first security key generates a scrambling vector for access to the voice communication. The scrambling vector is generated in accordance with the following operations:
(1) generating a second security key having first and second components using a first process having first and second input signals, the first input signal comprising the first security key and the second input signal comprising at least one of a transmit frequency and a receive frequency; and
(2) generating the scrambling vector responsive to the second security key.
The second MET tunes to the allocated frequency for the NET group using the scrambling vector to gain access thereto.
In another embodiment of the invention, the system further provides dual standby operation permitting voice communication alternately between a closed user group arrangement (NET radio) and a mobile telephone service (MTS). At least one of the first and second METs implement the function of responding either to a MTS page request indicating the mobile telephone service is being requested or to a NET radio channel assignment request as transmitted on a GC-S channel. When one of the first or second METs responds to a service request of either the closed user group arrangement or the mobile telephone service, the first or second MET is not required to monitor the GC-S channel for service requests for the other service.
In accordance with another embodiment, a mobile communication system receives and/or transmits a message from/to a mobile communication device. The system provides communication between multiple users in a closed user group arrangement. The system includes first and second mobile communication devices responsively communicable in the mobile communication system, and adapted to select a closed user group network identifier (NET ID) representing a NET group, and a controller responsively connectable to the first and second mobile communication devices. The at least first and second mobile communication devices are also adapted to transmit a priority message to the NET group and/or a priority NET group. The NET group and/or the priority NET group are adapted to receive the priority message as the communication in the closed user group arrangement.
In accordance with another embodiment of the invention, a mobile communication system provides communication between multiple users in a closed user group arrangement. The system includes first and second mobile communication devices responsively communicable in the mobile communication system, and adapted to select a closed user group network identifier (NET ID) representing a NET group including, for example, the first and second METs. The system also includes a controller adapted to receive the NET ID from the first mobile communication device, allocate a frequency for the NET group, and transmit the message to the NET group to inform the NET group of the allocated frequency. The second mobile communication device is adapted to tune to the allocated frequency in response to receiving the message. One the first and second mobile communication devices is designatable as a speaker for the NET group. At least one of the first and second mobile communication devices is also adapted to generate a security message for authorized access to the communication, and to tune to the allocated frequency for the NET group using the security message.
In accordance with another embodiment of the invention, a mobile communication system provides communication between multiple users in a closed user group arrangement. The system includes first and second mobile devices adapted to select a closed user group network identifier (NET ID) representing a NET group including, for example, the first and second mobile devices. The system also includes a controller adapted to receive the NET ID from the first mobile device, allocate a frequency for the NET group, and transmit the message to the NET group to inform the NET group of the allocated frequency and the communication associated therewith. The second mobile device is adapted to tune to the frequency in response to receiving the message, and one of the first and second mobile devices, for example, is designatable as a speaker for the NET group. The system is also adapted to provide dual standby operation permitting communication between, for example, the first and second mobile devices in at least one of the closed user group arrangement (NET radio) and a mobile telephone service (MTS).
These together with other objects and advantages which will be subsequently apparent, reside in the details of construction and operation as more fully herein described and claimed, with reference being had to the accompanying drawings forming a part hereof wherein like numerals refer to like elements throughout.